Monitoring the prevalence of thyroid disorders in the adult population of Northeast Germany

Abstract

BackgroundOnly a few studies like ours have investigated the effect of long-term stable iodine supply on thyroid disorders in a historically iodine-deficient population, but not with a long follow-up time of 10 years.MethodsData were derived from two independent population-based cohorts of the Study of Health in Pomerania (SHIP-0 [1997–2001] and SHIP-TREND [2008–2012]) comprising 4308 and 4420 subjects, respectively. Diagnosed thyroid disorders were assessed. Thyroid gland dimensions were examined by ultrasound. Levels of serum thyrotropin (TSH) and autoantibodies to thyroperoxidase (anti-TPO Abs) were measured from blood samples.ResultsMedian urinary iodine excretion levels decreased from 123.0 μg/l to 112.0 μg/l (p = <0.001) between 2000 and 2010. The prevalence of known thyroid disorders increased from 7.6 % [CI 6.9–8.5] to 18.9 % [CI 17.6–20.1] and of thyroid medication use from 6.2 to 11.1 %. The prevalence of goiter decreased from 35.1 to 29.4 % (p = <0.001), while the prevalence of positive anti-TPO Abs decreased from 3.9 to 2.9 % (p = 0.022). Median serum TSH levels increased from 0.69 mIU/L to 1.19 mIU/L (p = <0.001). Consequently, prevalence of high TSH (mIU/L) increased from 2.6 to 2.9 % (p = 0.452), and low TSH (mIU/L) decreased from 6.6 to 6.4 % (p = 0.737).ConclusionThe decreased prevalence of iodine-deficient disorders and a stable prevalence of markers of autoimmune thyroid disorders argue for an improved iodine supply of the adult population in Northeast Germany. In contrast, the prevalence of diagnosed thyroid disorders and the intake of thyroid medication increased, although this might be related to inappropriate therapeutic decisions.Electronic supplementary materialThe online version of this article (doi:10.1186/s12963-016-0111-3) contains supplementary material, which is available to authorized users.

Excess iodine intake: sources, assessment, and effects on thyroid function

“…However, other studies report no increase or a reduction in thyroid autoimmunity with time following fortification . The analysis of epidemiological data from a mildly iodine‐deficient population in Tasmania found no association between iodine supplementation and an increase of thyroid autoimmunity between 1995 and 2013 …”

“…However, other studies report no increase or a reduction in thyroid autoimmunity with time following fortification. 113,154,[156][157][158] The analysis of epidemiological data from a mildly iodinedeficient population in Tasmania found no association between iodine supplementation and an increase of thyroid autoimmunity between 1995 and 2013. 158 Improved diagnostic criteria and increasing the use of screening technologies for the thyroid (particularly thyroid ultrasound) have led to increased detection of mild thyroid disorders; this has likely contributed to an increase in the incidence of thyroid disorders and biased comparison over time.…”

Frequency of thyroid function tests and examinations in participants of a population-based study

“…Undiagnosed thyroid disorders (morphological or functional) are found in up to 75% of the population [4,5]. Thyroid nodules are detected in 30 to 68% [4,6,7], most of them as incidental findings [2,8,9]. Some studies observed an increasing prevalence of thyroid nodules, most likely due to an improved resolution of thyroid ultrasound devices, which are now able to detect thyroid nodules of 2 to 3 mm [2,6,7].…”

“…Thyroid nodules are detected in 30 to 68% [4,6,7], most of them as incidental findings [2,8,9]. Some studies observed an increasing prevalence of thyroid nodules, most likely due to an improved resolution of thyroid ultrasound devices, which are now able to detect thyroid nodules of 2 to 3 mm [2,6,7]. The Study of Health In Pomerania (SHIP) found elevated serum thyroid-stimulating hormone (TSH) levels in 4% and the Kooperative Gesundheitsforschung in der Region Augsburg (KORA) in 14% of study participants.…”

“…After an iodine fortification program was implemented in 1993 [6], goitre prevalence of the adult population in northeast Germany decreased from 35 to 30% [6] and in the age-group 11-17 years from 36 to 9% [10], but still remains common. Between 2005 and 2016, prescription rates for thyroid medications in Germany increased from 17 million [11] to 27 million per year [12].…”